Method and apparatus for the gas injection into a metal bath



Oct. 25, 1966 P. METZ METHOD AND APPARATUS FOR THE GAS INJECTION INTO AMETAL BATH Filed Aug. 25. 1961 INVENTOR fazx/Zfleiz BY mm 7 M UnitedStates Patent 3,281,136 METHOD AND APPARATUS FOR THE GAS INJECTION INTOA METAL BATH Paul Metz, Dudelauge, Luxembourg, assignor to LARBED,Acieries Reuuies de Burbach-Eich-Dudelauge, Society Anonyme, LuxembourgFiled Aug. 25, 1961, Ser. No. 134,071 Claims priority, applicationLuxembourg, Sept. 12, 1960, 39,169 1 Claim. (Cl. 266-34) The presentinvention relates to a process and an apparatus for the gas injectioninto a metal bath.

In the processes using injection from the top, in a metal bath by meansof a lance, of a jet of oxidizing gas which may carry in suspensionpowdered or granulated solid materials, it is proposed when it isdesired to cause the spreading out of the jet issuing from the lance todisturb the flow by injecting into the principal gas jet near the noseof the lance, some peripheric secondary jets of gas converging towardsthe axes of the tuyere.

In certain arrangements the injection lance comprises two concentricconduits, the inner conduit feeding the principal jet constituted forexample by oxygen carrying in suspension pulverized lime while the outerconduit feeds the secondary jets of gas which may be different from thegas constituting the principal jet. This arrangement permitsestablishing or interrupting at will the secondary jets during the flowof the principal jet. There are processes for example, in refining inthe Martin furnace where it is suitable to reduce in a permanent mannerthe penetration of the principal jet in the metal bath. In fact, infurnaces provided with an arch such as a vaulted roof, as are the Martinfurnaces, the insufiiation in the bath of very penetrating gaseous jetscauses strong projections which reach the arch where they attackviolently.

According to the present invention these strong and violent projectionsare avoided by rendering the jet slightly penetrating during the entireduration of the blast, this result being obtained by disturbing its flowby means of secondary jets.

Certain arrangements permit the realization of this objective by meansof permanent maintenance of the feeding of the secondary jets.

However, the same effect can be obtained with the aid of a lance of moresimple construction which constitutes a second object of the presentinvention. The lance, object of the invention, comprises a singleconduit for admitting gas or the insufilated mixture and ischaracterized in that the principal gas jet and the secondary jetsserving to disturb the flow are both fed by the single conduit. To thatend, the single conduit admitting gas or the insufilated mixture isprovided at its open end with a convergent-divergent outlet tube ortuyere in the form of a spool or drum, engaged in the said conduit andwhich provides, between its own outer surface and the internal surfaceof the conduit, an annular chamber which is placed in communication by agroup of cylindrical orifices or preferably divergent conical orificeswith the outlet of the divergent part of the tuyere, on the one hand,and by another group of cylindrical or preferably convergent orconvergent-divergent channels with the outlet tube of the divergent partof the tuyere on the other 3,281,136 Patented Oct. 25, 1966 hand. Bythis arrangement the annular chamber is fed with gas taken from thecentral jet in the convergent zone of the outlet tube and there isestablished in the said chamber a pressure greater than the pressureprevailing below in the divergent part. Because of this fact, the gascontained in the annular chamber flows through channels debouching inthe divergent part of the outlet tube forming secondary jets with highspeed which disturb the principal jet and consequently reduce thefaculty of penetration in the metal bath of the resultant jet.

The axes of the secondary jets can meet at one and the same point of thegeometric axis of the outlet tube or, on the contrary, can be orientedtangentially to an axial geometric nucleus in such a way as to impart aprincipal gyratory motion.

According to the invention it is advantageous to dimension the orificesand the channels of the outlet tube in such a way that the entire flowof the secondary jets will be not less than 20% of the total.

It is clear that the gas insufllated by the lance may or may not beadmixed with pulverulent materials, as for example, lime.

By way of a non-restrictive example, the accompanying drawing shows as avertical section an injection lance cooled by water circulation inaccordance with the invention.

In the drawing, 1 designates the single conduit admitting the gas to beinsufllated and Which contingently may carry pulverulent materials insuspension. 2 designates the outlet tube or tuyere comprising aconvergent part 3 at one end and a divergent part 4 at the other end. 5designates the chamber or space between the inner surface of the conduit1, and 6 designates the orifice-s pierced near the entrance section ofthe convergent part 3 of the outlet tube 1. 7 designates channelspierced in the wall of the outlet tube near the outgoing section of thedivergent part 4.

The axes of the channels 7 are disposed obliquely with respect to theaxis of the tuyere, and their axes may or may not intersect the axis ofthe tuyere.

Owing to the convergent-divergent form of the central conduit of theoutlet tube the pressure of the gas at the level A is greater than thegaseous pressure at the level B.

The total area of the orifices 6 being greater than the total area ofthe channels 7, the pressure established in the annular chamber 5 willbe substantially equal to the pressure prevailing at the level A in theoutlet tuyere 2. It follows that the pressure at the entrance of thechannels 7 is about the same as the pressure prevailing at the level A,while at the outlet of the channels there prevails the pressure of thecentral jet at the level B which is, as stated, distinctly lower thanthe gaseous pressure at level A.

Consequently the secondary jets which flow through the channels 7 intothe central or principal jet of the outlet tube are endowed with a greatspeed which renders them capable of effectively disturbing the saidcentral jet, that is to say, to disperse the gases and/or the particlesleaving the orifice of the outlet tube making them deviate in divergentdirections.

I claim:

A device for injecting an oxidizing gas into a metal bath comprising aconduit feeding gas at its open end provided with a convergent-divergenttuyere engaged in the said conduit and which provides between its ownexternal surface and the internal surface of the tuyere an annularchamber which is in communication by a group of orifices of conical anddivergent configuration with the upper part of the convergent of thetuyere and convergent-divergent channel-s in the tuyere with the lowerpart of the divergence of the tuyere, said channels being orientedobliquely and convergently with respect to the axis of the tuyere.

References Cited by the Examiner UNITED STATES PATENTS Lataste 239 s43 x15 3,130,252 4/1964 Metz 26635 FOREIGN PATENTS 962,937 12/ 1949 France.685,715 12/1939 Germany.

3,449 1877 Great Britain. 254,603 7/ 1926 Great Britain. 667,654 3 195 2Great Britain.

CHARLIE T. MOON, Primary Examiner.

WINSTON A. DOUGLAS, Examiner.

I. C. HOLMAN, B. E. LAKE, P. M. COHEN,

Assistant Examiners.

